


Mechanical Fantasy

by Deeranger



Category: Supernatural
Genre: Anal, Anal Fingering, Anal Sex, Bottom Sam, Bottom Sam Winchester, Dominance, First Time, Forbidden Love, Hand Jobs, Incest, M/M, Mechanic Dean Winchester, Outdoor Sex, Pining, Sam Winchester in Love, Secret Crush, Sex in/on the Impala (Supernatural), Sex on a Car, Sexual Fantasy, Sibling Incest, Smut, Top Dean Winchester, Tumblr Ask Box Fic, Tumblr Prompt, Young Sam Winchester
Language: English
Status: Completed
Published: 2020-04-09
Updated: 2020-04-09
Packaged: 2021-03-02 00:15:08
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,935
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23565916
Author URL: https://archiveofourown.org/users/Deeranger/pseuds/Deeranger
Summary: Sam is in love. With his brother. And he knows how wrong that is. So, he has to imagine what he can't have, doesn't he?
Relationships: Dean Winchester/Sam Winchester
Comments: 8
Kudos: 166





	Mechanical Fantasy

**Author's Note:**

> Based on the Tumblr askbox prompt: Sam's secret sex fantasy about Dean?

_**Closing his eyes Sam’s hand slip under the covers, trying to be as silent as possible. His brows furrow as he paints his favorite image inside his mind, and he tries to keep his breathing steady…**_

His big brother would be leaned over the open hood, muscles rippling under his freckled skin as he works on the Impala’s engine tirelessly. And those muscles... All firm and glistening with both sweat and streaks of oil every time he moves. Sam would feel all breathless, standing next to him with a cool Budweiser in his hand and just watching his brother’s hands expertly fix the camshaft. He doesn’t even know what the hell a camshaft is or what it does, but the way Dean’s hands roam over it? It makes the young Winchester wish that those hands were all over _him_ instead. As heat rise in Sam’s cheeks he tries to just act normal. His brother can’t know.   
  


“Can I have a sip of that?” Dean asks, startling the young man and ripping him from his train of thought. At first Sam doesn’t even realize that he’s referring to the Bud in his hand that grows staler by the minute - he has forgotten all about it.   
  


“Uhh, yeah... Sure,” Sam says and hands him the bottle. As it switches hands Dean’s calloused fingers brush over his and he holds back a tiny gasp. And then his big brother puts the bottle to his lips, gulping down big mouthfuls of beer. Watching those full lips wrap around the glass has Sam squeezing his thighs together when suddenly he feels himself chubbing up underneath the denim of his jeans. _‘Oh god, no,’_ he thinks to himself frantically. _‘Not now!’  
  
_

“Thanks, Sammy,” Dean says and gives him back the bottle. The tiny droplets still clinging to his full bottom lip makes Sam swallow down a whimper. What would those lips feel like? They would probably be soft as velvet, wouldn’t they? _‘Stop it!’_ Sam tells himself and blushes an even deeper pink. And this time he has to turn a little to hide his growing erection. Flustered he swallows dryly:  
  


“Umm, I’m just gonna... Gonna go inside,” he says and turns to leave.  
  


“Why? Aren’t you having fun?” Dean asks, straightening up to look at him. Embarrassment washes through Sam along with an overwhelming feeling of nervousness. What if Dean sees how aroused he is? Oh god, this is so wrong.   
  


“Yeah, I, uh... I just need to go to the bathroom,” he says and he hates how his voice almost trembles. _‘Keep it together!’_ the little voice in his head screams at him and he takes a step away from the car.  
  


“No, you’re not,” Dean says and in the same moment a hand grips his wrist, stopping him dead in his tracks. This time he can’t suppress the tiniest of gasps from slipping out of his mouth. Dean’s touch feels like electrified feathers dancing across his skin and his heart skips a beat.  
  


“Stay,” Dean just says, looking him straight in the eye. Confused and bewildered Sam instantly casts down his gaze, not quite able to stay locked in eye contact with his brother right now. 

  
“I know you like watching me fix things,” his older brother dead-pans and instantly it feels like Sam’s heart jumps all the way up to lodge itself somewhere near his Adam’s apple. _‘What does he mean?’_ his mind shrieks, but he doesn’t dare to ask. Not even by a long shot.  
  


“Don’t you, Sammy?” Dean asks. And Sam swears that his face must be as red as a tomato by now. _‘Just stay cool!’_ he thinks to himself, not quite sure how to answer. But clearly his brother wants him to, because he has stopped working on the car.

  
“Y-Yeah...” he stutters, squeezing his legs even closer together. A smirk tugs on Dean’s lips and suddenly he pulls on Sam’s wrist, yanking him back to the car and turning him around to bend over the open hood. A whine escapes the young Winchester and he freezes comepletely when he feels his brother lean over him from behind, his big hands grabbing his own and putting the empty beer bottle aside.  
  


“Look, all you gotta do... Is crank this a bit to the right,” Dean says and guides Sam’s hand to do as he instructs. As his big hands work on top of his, oil is getting smeared everywhere and Sam is starting to sweat profusely, his mind a whirl of thoughts. Forbidden thoughts. Thoughts that he shouldn’t at all be thinking when it’s his brother pressed against him like this. 

  
“And then... You screw this off,” Dean says, hot breath fanning across the shell of Sam’s ear as he helps him work on the engine. By now Sam has to focus for his hands not to shake and his erection is painfully pressing against the sleek, black metal of the car. Maybe that’s a good thing. Maybe the pain will make it go away.   
  


“Rub it,” Dean instructs, and Sam swears that he can hear a new kind of tone to his brother’s gravelly voice. Like it has dropped just a little bit lower. But he’s probably just imagining it. Swallowing he rubs the best that he can, the pad of his thumb cleaning away dust and oil spatters.   
  


“Good... That’s good,” his brother says and moves a little closer, now pressed flush against Sam - so close that Sam can smell his cologne, the cheap shampoo he uses and just a whiff of bourbon. But that’s not what he focuses on. Because now he thinks he feels a hardness lightly poking him, the bulge in his brother’s jeans pressing against his rear and making his pulse skyrocket. 

  
“Now put it back on,” Dean says, and Sam thinks he sounds just a bit out of breath. And he isn’t exactly innocent of that either, he discovers - because his breath is coming out in quick and shallow puffs of air as he shakily convinces his hands to follow Dean’s lead and screw the metal contraption back on. An appreciative noise leaves Dean, and Sam nearly shudders as arousal ripples through him anew, the sound of Dean’s voice so close to his ear making it feel like it’s rumbling through his entire body.

  
“Now we gotta go up here...” Dean says under his breath and moves Sam’s hands up towards the opposite side of the engine, making him stretch over almost all of the width of the car. As Dean follows him, putting a little weight on Sam’s back the young hunter can’t help but let out a small, high-pitched sound when his erection is squashed against the side of the car. But it doesn’t really hurt. Not that much, anyway. The stimulation - even though slightly painful - is better than none at all. _‘What’re you doing!?’_ his mind spits at him, angry that he can’t seem to control his body.  
  


“See that emission valve?” Dean asks softly, and Sam’s breath hitches in his throat when his brother rolls his hips just a little, pressing against him a bit harder. And now there’s no doubt in Sam’s mind. His brother is hard. And not just a little bit; no, he’s got a raging hard-on and it’s pressing right at Sam’s denim-clad ass.   
  


“Umm...” Sam croaks, not able to find any of the words he was going to say. Because nothing inside his head seems to be working right now, everything is just a frantic whirl of arousal and shame and fear and more arousal.  
  


“See it? Right there,” Dean says and guides Sam’s hand to the valve, making him grip it.   
  


“Y-Yeah…” Sam manages to rasp, and he bites his bottom lip when suddenly one of Dean’s hands disappears from his. But before two seconds have passed it returns, stuffing a piece of cloth in between Sam’s fingers carefully.  
  


“It needs cleaning. Think you can do that?” Dean whispers in his ear, and Sam can feel a full body shudder roll through him. Unable to speak he just nods his head, forcing his shaking fingers to rub the cloth against the dirty metal. And then Dean’s hand disappears again – but this time it isn’t to pick up a spare part, cleaning supplies or beer. This time it trails down Sam’s side only to settle on to his hip, softly grabbing it. Instantly the young Winchester sucks in a gulp of air, his heart racing so fast that he can’t even keep track of the beats.  
  


“Just keep going…” Dean says and Sam realizes that he has stopped moving his hand. Out of breath he picks back up, rubbing the white fabric over the metal and picking up black oil and greasy dust.  
  


“That’s it,” his brother says and hooks two fingers around the waistband of Sam’s jeans, beginning to tug them down his legs. In that moment it feels like both of them forget how to breathe, and Sam barely manages to stop a wanton whine from rushing out of his mouth.  
  


“See, oil isn’t supposed to go on the valves…” Dean explains as Sam’s jeans slowly get tugged lower and lower, sliding down over his hips and exposing skin full of goosebumps despite the blazing summer sun. When the waistband catches on his erection it can’t go any further, and Sam snaps for air as his dick gets nudged at the base. Carefully Dean pulls Sam out from the car just a little bit – but just enough to maneuver the jeans past his throbbing length – only to push him back against the metal. As his jeans fall down his long legs, exposing him, Sam fails to hold back a breathless moan.  
  


“Know how oil works in a car, Sammy?” Dean asks in a throaty voice, and the young Winchester suppresses the urge to press his ass against the bulge in his brother’s jeans. Instead, he weakly manages to shake his head.

  
“Well, it gives life to an engine. Kind of like how blood works in a body,” Dean says, and now Sam doesn’t doubt that his voice has dropped into an even deeper register. He has never heard him like this before, but damn, it goes straight to his dick. Pre-cum is getting smeared against the black metal of the Impala when Dean’s free hand slides down his hip only to grab his ass cheek, gently kneading it in his big palm. Another whine escapes Sam and he really has to focus everything he has got to keep from coming right here and now.

  
“You have the sump where the bulk of the oil is stored… And then you have oil galleries, and those are just like the veins that transport blood around your body…” Dean says lowly, slipping a wet index finger in between Sam’s ass cheeks. Nearly jumping from the touch Sam lets out a wheezy gasp, trying not to let his hand stop its cleaning. By now sweat is beading everywhere on his skin, and he shivers as the tip of his brother’s finger nudges at his entrance. _‘Oh, god!’_ his mind blurts out, and he tries to gather his thoughts, tries to stay still, but it’s hard not to mindlessly seek out friction for his touch-deprived dick. He really wants to rut against the Impala, wants to feel some more friction – but he doesn’t dare. 

  
“Then you have the oil pump… Which is just like the heart,” Dean whispers and wiggles his fingertip a little. As it rubs against the furled muscle, slick with something Sam guesses must be oil or grease, he can’t help but arch his back a little, pushing back against his brother. As the pressure increases Dean lets his fingertip slip inside and instantly Sam lets out a shaky moan. It feels like his groin is on fire, like a coil is threatening to snap at any moment.

  
“And then… Then you have the filter…” Dean says, his voice husky and sounding strained as he pushes the finger in deeper, seemingly enjoying how the tight heat clamps down on him like a vice.

  
“The filter is just like the kidneys… Removing impurities before it’s pumped through the system,” he says, and this time there’s a hint of a moan accompanying his voice when his finger can’t go in any deeper and he begins to pull it back out. Shivering Sam can’t help but let out a grunt and he finds himself rutting against the cool metal of the Impala, his cheeks burning a bright shade of magenta.  
  


“Fuck, Sammy…” Dean whispers, closing his hand around Sam’s on top of the engine block when his finger slips out of him, eliciting a whine from his little brother. Still stretched over the car Sam’s other hand has stopped rubbing the cloth against the valve – instead it’s just clutching the metal like he is clinging on to it for dear life.

  
“Please… Dean...” he hears himself moan, and the magenta in his cheeks turns close to crimson. He gets a grunt in response and he can feel his brother fumbling to undo his jeans, gravel crunching under him as he moves. Instantly a new spike of arousal shoots through the young Winchester and he wants to turn his head and look – but he can’t. And he’s not sure if he wants to, because he’s terrified of ruining the moment.

  
“Don’t move,” his brother says – as if he can read his mind. And suddenly something slick is being drizzled down the cleft of his ass and rubbed over his hole, making him shake with anticipation. _‘This is happening!?’_ his mind whispers excitedly somewhere in a dark corner of his mind and he feels how the fire in his loins instantly grows more intense when Dean begins to press against him.  
  


“Oh, god…!” Sam bursts out in a whine when he feels the flared head of his brother’s cock nudge him, lightly pressing. His own cock is already leaking, drooling impressive amounts of pre-cum onto the Impala’s paint and making a mess. His thighs are shaking and his entire body goes stiff from excitement when Dean clutches his hand a little harder.  
  


“Relax for me, okay?”  
  


His big brother’s voice sounds impossibly husky, all deep and rumbling like thunder, but still it sounds just as compassionate as wanton somehow. Sam nods his head jerkily and wants to spread his legs wider – but he discovers that he can’t because of the jeans pooling around his ankles. Dean doesn’t seem to mind though and as Sam shakily exhales, relaxing his body, his big brother finally rolls his hips. The movement is calculated. It’s firm but still slow enough to avoid startling Sam or forcing his walls to expand too fast – and as the head of Dean’s cock slips inside, both brothers let out a loud groan.

  
“Oh, f-fuck…! Dean…!” Sam moans, feeling the burn and the stretch as his brother pushes inside just a bit deeper. It feels like he’s being split in two, but the sting is delightful and the pleasure overrides the pain. Basically draped over his back Dean breathes hard against the shell of his ear, seemingly trying to keep his composure.  
  


“Like that, Sammy? Like my cock splitting you open?” he moans and Sam’s dick twitches at the vulgar words.

  
“Y-Yes…! Yes!” he grunts, pushing back against Dean and driving him in another inch. Once again a moan escape both of them and this time Dean lets go of Sam’s hand to grab his hip.

  
“Shit… Oh, god…!” Dean grits out and stills a bit, his face scrunched up in what looks like a mix between agony and ecstasy. Sam lets out another moan, wiggling his hips a little in the attempt to get Dean to move.  
  


“Please! Please, Dean, just fuck me…!” he babbles, mind gone in a whirlwind of lust. And his brother lets out a shaky breath, fingertips on both of his hands digging into Sam’s hips. And then he rolls his hips again. As the last long inches slip inside the tight channel and drag against Sam’s insides, heavy balls come to rest against his skin with a slapping sound as Dean bottoms out. Fully seated in his little brother he lets out a strangled groan coming from somewhere deep in his chest, and it almost drowns out the whine escaping Sam.

  
“Oh, I’ll fuck you…” Dean whispers, tightening his grip on Sam’s hips so hard that it’s bound to leave a mark.  
  


“Been thinkin’ of doing this for so long,” he adds as he begins to pull back out, the spongy head of his dick pulling on the narrow and quivering walls and ripping a hiss from Sam’s throat. And then – just when the flared head catches on his little brother’s rim – he pushes back inside with a snap of his hips. As Sam is rocked forwards against the car he grips the valve tighter, knuckles turning a milky white, and he lets out a breathless moan.  
  


“Been thinkin’ ‘bout that sweet ass of yours for years, Sammy…!” Dean grunts, reaching around his brother to grab his dick. As soon as the thick fingers wrap around it, Sam sucks in a big gulp of air – and automatically he clenches around Dean, making him let out a another deep grunt.

  
“Gonna fuckin’ wreck you,” Dean whispers and gives Sam’s throbbing length a firm stroke. A gasp gets caught in the young Winchester’s throat when it feels like electric currents zap through him, spreading like fiery tendrils all the way up his spine. And then Dean moves. Without hesitation he sets a steady pace, fucking in and out of his brother with smooth thrusts, watching through hooded eyes how Sam practically writhes below him. And the heat is quickly building in Sam’s groin, burning, searing, blazing with each movement of Dean’s cock in his ass or the skilled hand on his dick.

  
“Dean! Fuck! Oh, god, please, don’t stop!” Sam bursts out, unintelligible begging spilling from him without him even registering it.

  
“Ain’t gonna stop, baby. Gonna give it to you so good!” Dean moans, rolling his hips in earnest and slamming against Sam with each forceful thrust, making the Impala’s suspension give off a creaking noise as it is rocked back and forth a little.

  
“Gonna make you cum in my hand… You’d like that, wouldn’t you?” Dean asks, watching in awe as his cock is swallowed by his brother’s ass over and over again. In, out, in, out in a rhythm that just grows faster and faster and more and more desperate as they both chase their orgasm.  
  


“Yes! Yes! Please make me cum!” Sam pants, bucking and thrusting into Dean’s fist. He doesn’t care that the tip of his dick hits the hard metal of the Impala, doesn’t even feel it. The only thing he can feel is the searing fire in his groin that is about to consume him completely, flames licking at his balls, his dick, everywhere – and the feeling of his brother’s thick cock impaling his ass.

  
“Yeah? I’ll make you fuckin’ cum…” Dean moans, speeding up his stroking. As calloused fingers rub up and down Sam’s shaft and the pad of a thumb occasionally swipes over his slit, the young Winchester can’t hold back a soft cry when he feels his balls draw up – and he mindlessly bucks his hips. 

  
“Cum for me, Sammy!” Dean commands, now tugging on his brother’s dick faster and firmer with skilled flicks of his wrist. As soon as the words reach Sam’s ears he tenses, his entire body going rigid and muscles cramping – and spurts of semen shoot from his dick in long ropes, splattering out on the Impala’s side and running down over Dean’s hand in sticky globs. Crying out his brother’s name Sam keeps spasming in an orgasmic white-out, and he clamps down on Dean so hard that it borders on being painful – and that little tinge of pain is all Dean needs. With a roar he tumbles over the edge as well, following his little brother into a climax so intense that he forgets to breathe. His hips stutter, thrusts growing jerky and erratic just before he pushes in as deep as he can possibly go. Hugged tight by Sam’s warm body, he feels himself grow bigger and impossibly hard and he comes with such force that all he can see is shimmering, white light filling his field of vision.

  
“F-Fuckkkk!!!” he growls as gushes of sperm fill Sam to the brim, trickling out around the base of his cock even though he is buried to the hilt. For a moment the world comes to a halt, everything suspended in pure bliss and white light as seconds slow down into something that feels like an eternity. Then, everything comes back, the bright white slowly diffusing and leaving Dean’s vision - and he collapses on top of his little brother.

  
For a long moment they just lie there, Dean’s face buried in the sweat-soaked hair at the back of Sam’s neck while they both focus on breathing. With his chest squashed against the many metal parts of the engine Sam should be uncomfortable, but somehow he isn’t. Instead, he feels like putty. Soft and melted and warm and sated. And for some strange reason his brother’s weight crushing him against the car makes a new spark of arousal shoot through him.

  
“Fuckin’ hell, Sammy…” Dean pants, his dick still inside of him and slowly shrinking. As it does more semen dribbles out to run down Sam’s inner thighs in sticky, white streams. Just breathing heavily Sam closes his eyes, memorizing every single detail. Mapping them, categorizing them and putting them in a hidden place in the darkest corner of his mind where no one can ever take them from him. Behind him Dean is trying to regain his composure, slowly lifting himself off of Sam’s back – as his dick begins to slip out him, Sam can’t hold it back anymore:

  
“I love you.”

  
The declaration hangs in the air, electric and loud and heavy. But he can’t take it back. And he won’t. Behind him Dean has stilled completely. Sam can’t even hear him breathe, he realizes. _‘Oh, god… Oh, no,’_ his mind cries somewhere, real fear beginning to spread when the words dissolve and get swallowed by silence. _‘What if, what if he doesn’t—‘_

  
“I love you too, Sam,” Dean says, shattering the silence into a thousand bits. Instantly it feels like a weight is lifted off Sam’s shoulders, like he is suddenly floating – like that black and tight knot of shame and fear in his gut is untangled only to be erased. Because his brother isn’t lying. He can tell by the new tremble in his voice, that rare vulnerability that he never really gets to hear. And a smile flutters to life on Sam’s face, a deep exhale getting punched out of him when relief washes through him. Because his brother loves him. His brother actually loves him. For real.   
  


**_… A quiet sigh slips out of Sam’s mouth as he carefully opens his eyes. His underwear is a sticky mess, and so is his hand – so, he thoroughly wipes it on the inside of his trunks, trying to rid his fingers of his own release. Slowly he turns his head to the side; his brother is still asleep. Thank god. A heavy sort of sadness mixes with post-orgasmic haze, and he decides that he better tiptoe to the bathroom to change his soiled underwear. Dean can’t find out, after all._ **

****


End file.
